February 16, 2005
02:00 PM (EST)

News Release Number: STScI-2005-06

Saturn's Auroras Defy Scientists' Expectations

February 16, 2005: The dancing light of the auroras on Saturn behaves in ways different
from how scientists have thought possible for the last 25 years. New
research by a team of astronomers led by John Clarke of Boston
University has overturned theories about how Saturn's magnetic field
behaves and how its auroras are generated.

Q & A: Understanding the Discovery

1.
What are auroras?

Auroras are initiated when charged particles in space collide with a
planet's magnetic field and stream into the upper atmosphere. Collisions
with gases in the planet's atmosphere produce flashes of glowing energy
in the form of radio waves and light (visible, ultraviolet, and
infrared). Seen from space, an aurora appears as a ring of light
circling a planet's polar region, where magnetic poles typically reside.

2.
What is a magnetic field?

A magnetic field is a region of space in which magnetic forces may be
detected or may affect the motion of an electrically charged particle.
Earth has a magnetic field. One way to see the effects of the Earth's
magnetic field is by using a compass. The needle on a compass always
points north, because the influence of the Earth's magnetic field forces
the metal needle to point toward the Earth's magnetic pole. The same
effect occurs with charged particles (ions and electrons) around Earth.
They are forced to move toward the magnetic north or south pole.

3.
Do all solar-system planets have magnetic fields?

The Earth and all of the giant planets (Jupiter, Saturn, Uranus, and
Neptune) have magnetic fields. Venus does not, and Mars has only very
weak, local magnetic effects.

4.
Why do some planets have auroras and others do not?

Auroral storms are a normal phenomenon. They occur whenever a magnetic
field is present to direct charged particles into a planet's atmosphere
where they interact with atmospheric gases and make them glow. Every
planet with a magnetic field and an atmosphere has an aurora.